The present invention relates generally to a projection-type color display device and, in particular, to a projection-type display device which uses a color synthesis cube prism to synthesize separate, modulated monochromatic lights for improving the projection of images.
Conventional projection-type display devices have synthesized only monochromatic images through the use of reflective light-valves and dichroic mirror groups, for example, as disclosed in Japanese Laid-Open patent application No. 58-180937.
The conventional projection-type color display devices have several deficiencies. In a device using reflecting light valves, first, the reflected light at the surface of the light valve causes deterioration of the contrast of the displayed images. Second, since the light-valves are addressed by the light from a cathode ray tube (CRT), the device is required to be large. Third, an excellent polarized light separation quality of the dichroic mirror is required.
The present invention was developed to solve the aforenoted problems. Accordingly, it is desired to provide an improved projection-type color display device.